The major goal of this proposal is to characterize the microbial population involved in organic solvent degradation within Aberjona Watershed. A knowledge of these characteristics will tell us of the factors that are limiting solvent degradation as well as the features of the population which encourage degradation. It is only through an understanding of the native population rather than through a study of pure cultures that we can hope to improve the degradative process. Biodegradation is clearly the dominant process for removal of organic solvents in groundwater and is very important in surface waters. These are naturally occurring processes and with time will remove some of the solvents contaminating surface and groundwaters. The first goal of this study is to determine solvent degradation rates for natural samples from the watershed. Results will tell us of the natural capacity for solvent degradation by the indigenous microbial population. Along with the studies of Profs. Gschwend, Gelhar and Hemond these data will allow us to predict the fate of solvents in these environments. The second phase of this proposal involves a study of solvent degradation in simulated environments (laboratory scale). The resident microbial population in these environments will be studied to determine the heterogeneity of the population and characterize the key microbes involved in solvent degradation. This population is likely to be made up of a variety of microorganisms of which many may be indirectly involved in solvent degradation. It is our goal to characterize the population to an extent that will allow us to understand the major microbial interactions among the resident microorganisms.